Flux enhancement in the inner region of a geometrically and optically thick accretion disk

The surface flux (and the corresponding observed flux) of a geometrically thick ``funnel'' shaped disk is computed taking into account the radiation impinging on the surface from other parts of the disk. It is found that the ratio of the maximum apparent luminosity to the real luminosity of the disk is only a factor $\approx 5$ even when the opening angle of the disk is small ($\approx 15^o$). Thus, geometrically beamed emission from ``funnel'' shaped sub-Eddington disks around stellar mass black holes, cannot explain the Ultra-Luminous X-ray sources detected in nearby galaxies.Comment: accepted for publication in Ap

The Kelvin Formula for Thermopower

Thermoelectrics are important in physics, engineering, and material science due to their useful applications and inherent theoretical difficulty, especially in strongly correlated materials. Here we reexamine the framework for calculating the thermopower, inspired by ideas of Lord Kelvin from 1854. We find an approximate but concise expression, which we term as the Kelvin formula for the the Seebeck coefficient. According to this formula, the Seebeck coefficient is given as the particle number $N$ derivative of the entropy $\Sigma$, at constant volume $V$ and temperature $T$, $S_{\text{Kelvin}}=\frac{1}{q_e}\{\frac{\partial {\Sigma}}{\partial N} \}_{V,T}$. This formula is shown to be competitive compared to other approximations in various contexts including strongly correlated systems. We finally connect to a recent thermopower calculation for non-Abelian fractional quantum Hall states, where we point out that the Kelvin formula is exact.Comment: 6 pages, 2 figure

Spatiotemporal rheochaos in nematic hydrodynamics

Motivated by the observation of rheochaos in sheared wormlike micelles [Bandyopadhyay et al., Phys. Rev. Lett, 84 2022, (2000); Europhys. Lett. 56, 447 (2001); Pramana 53, 223 (1999)] we study the coupled nonlinear partial differential equations for the hydrodynamic velocity and order parameter fields in a sheared nematogenic fluid. In a suitable parameter range, we find irregular, dynamic shear-banding and establish by decisive numerical tests that the chaos we observe in the model is spatiotemporal in nature.Comment: Slight changes in text, references and Fig. 5 inset; 6 eps figures (figs 2,3,4 at lower resolution to reduce file size; full files available on request); accepted for publication in Phys Rev Let

Finite temperature properties of the triangular lattice t-J model, applications to Nax_xCoO2_2

We present a finite temperature ($T$) study of the t-J model on the two-dimensional triangular lattice for the negative hopping $t$, as relevant for the electron-doped Na$_x$CoO$_2$ (NCO). To understand several aspects of this system, we study the $T$-dependent chemical potential, specific heat, magnetic susceptibility, and the dynamic Hall-coefficient across the entire doping range. We show systematically, how this simplest model for strongly correlated electrons describes a crossover as function of doping ($x$) from a Pauli-like weakly spin-correlated metal close to the band-limit (density $n=2$) to the Curie-Weiss metallic phase ($1.5<n<1.75$) with pronounced anti-ferromagnetic (AFM) correlations at low temperatures and Curie-Weiss type behavior in the high-temperature regime. Upon further reduction of the doping, a new energy scale, dominated by spin-interactions ($J$) emerges (apparent both in specific heat and susceptibility) and we identify an effective interaction $J_{eff}(x)$, valid across the entire doping range. This is distinct from Anderson's formula, as we choose here $t<0$, hence the opposite sign of the usual Nagaoka-ferromagnetic situation. This expression includes the subtle effect of weak kinetic AFM - as encountered in the infinitely correlated situation ($U=\infty$). By explicit computation of the Kubo-formulae, we address the question of practical relevance of the high-frequency expression for the Hall coefficient $R_H^*$. We hope to clarify some open questions concerning the applicability of the t-J model to real experimental situations through this study

Magnetic Raman scattering from 1D antiferromagnets

We study Raman scattering from 1D antiferromagnets within the Fleury-Loudon scheme by applying a finite temperature Lanczos method to a 1D spin-half Heisenberg model with nearest-neighbor ( J1) and second-neighbor ( J2) interactions. The low-temperature spectra are analyzed in terms of the known elementary excitations of the system for J2 = 0 and J2 = ½. We find that the low- T Raman spectra are very broad for |J2/J1|≤0.3. This broad peak gradually diminishes and shifts with temperature, so that at T &gt; J1 the spectra are narrower and peaked at low frequencies. The experimental spectra for CuGeO3 are discussed in light of our calculations

Short-course chemotherapy for tuberculosis of the spine : A comparison between ambulant treatment and radical surgery - a ten year report.

We perfomed a randomised, controlled clinical trial to compare ambulant short-course chemotherapy with anterior spinal fusion plus short-course chemotherapy for spinal tuberculosis without paraplegia. Patients with active disease of vertebral bodies were randomly allocated to one of three regimens: a) radical anterior resection with bone grafting plus six months of daily isoniazid plus rifampicin (Rad6); b) ambulant chemotherapy for six months with daily isoniazid plus rifampicin (Amb6); or c) similar to b) but with chemotherapy for nine months (Amb9). Ten years from the onset of treatment, 90% of 78 Rad6, 94% of 78 Amb6 and 99% of 79 Amb9 patients had a favourable status. Ambulant chemotherapy for a period of six months with daily isoniazid plus rifampicin (Amb6) was an effective treatment for spinal tuberculosis except in patients aged less than 15 years with an initial angle of kyphosis of more than 30° whose kyphosis increased substantially

A prospective study of effect of amniotic fluid index less than 5 at term on perinatal outcome

Background: To study the effect of oligohydramnios in pregnancy and its value in predicting adverse perinatal outcome.Methods: A prospective case control study of pregnancy outcome in 100 cases with ultrasound diagnosis of oligohydramnios at term compared with 100 controls with no oligohydramnios. The study was done over a period of 3 years at SSMC Tumkur, India.Results: Oligohydramnios at term is associated with poor perinatal outcome. Significant increase in abnormal foetal heart rate, meconium stained liquor, delivery by cesarean section, low Apgar intrauterine growth restriction (IUGR), increased admissions to  neonatal intensive-care unit (NICU) were seen in study group, however perinatal mortality was more in study group but not statistically significant (P=0.31)Conclusions: AFI <5 at term is an important fetal surveillance methods to identify poor perinatal outcome and thereby makes possible intervention so as to reduce perinatal morbidity and mortality

Role of Doppler indices of umbilical and middle cerebral artery in prediction of perinatal outcome in preeclampsia

Background: Hypertension which develops de novo in pregnancy appears to be unique to human and continue to be a major cause of reported perinatal mortality. The aim and objectives of the study was to evaluate the diagnostic value of Umbilical and Middle cerebral artery Doppler in predicting the perinatal outcome in preeclampsia.Methods: A prospective study at Sri Siddhartha Medical College and Hospital between October2013-September2015 on 80pregnant women with preeclampsia at &gt;30weeks gestation. Studies of fetal vessels were performed using a pulsed Doppler ultrasound. Resistance Index (RI), Pulsatility Index (PI) and systolic/diastolic ratio (S/D) were measured in umbilical artery (UA) and Middle cerebral artery (MCA) and perinatal outcomes were monitored and statistically analyzed.Results: Out of 80 cases studied, 25 cases showed adverse perinatal outcome, among which 6 cases with perinatal death, 13 cases had low APGAR at 5minutes. 6 cases had NICU admission.Conclusions: Color Doppler has an important role in antepartum fetal surveillance in preeclampsia which can detect fetal compromise at an early stage. In our study pulsatility index of umbilical artery and ratio of MCA/UA PI was more sensitive than other parameters with PPV 78%

HLA-DR2 subtypes & immune responses in pulmonary tuberculosis

Background & objectives: HLA-DR2 has been shown to be associated with the susceptibility to pulmonary tuberculosis and altered antibody and lymphocyte response in pulmonary tuberculosis. In the present study, the influence of DR2 subtypes on antibody titre and lymphocyte response ,to Mycobacterium tuberculosis culture filtrate antigens (10 μg/ml) was studied in 22 patients with active pulmonary TB (ATB), 50 inactive (cured) TB (ITB) patients and 36 healthy control subjects. Methods. HLA-DR2 gene was amplified by polymerase chain reaction (PCR) and dot-blotted. Genotyping of DRBl*1501, *1502, *1503, *1601 and *1602 was carried out using sequence specific oligonucleotide probes (SSOPs) and detected by chemiluminescence method. Antibody titre as well as lymphocyte response to M.tuberculosis antigens were measured by enzyme linked immunosorbent assay (ELISA) and lymphocyte transformation test (LTT) respectively. Results: The allele frequency of DRB1*15Ol was significantly increased in pulmonary tuberculosis patients as compared to controls (P<0.05). No marked difference in the antibody titre and lymphocyte response to M. tuberculosis antigens was observed between the DRBl *1501, *1502 and *1503 positive or negative controls, ATB and ITB patients. DRBl *1501 and *1502 positive as well as negative ATB patients showed a higher antibody titre as compared to controls and ITB patients. ITB patients with *1502 showed a higher lymphocyte response as compared to *1502 positive controls (P<0.001) and ATB patients (P<0.05). Similarly, an increased lymphocyte response was observed in *1501, and *I503 negative ITB patients compared to *1501 and *1503 negative controls and ATB patients. Interpretation & conclusion: The present study revealed that DRBl *1501 may be associated either alone or with other DR2 alleles, with the susceptibility to pulmonary tuberculosis. None of the DR2 alleles influenced the antibody and lymphocyte response to M tuberculosis culture filtrate antigens. This suggested that HLA-DR2 gene/gene products as a whole may influence the immune response in pulmonary tuberculosis

Nanocolumnar Preferentially Oriented PSZT Thin Films Deposited on Thermally Grown Silicon Dioxide

We report the first instance of deposition of preferentially oriented, nanocrystalline, and nanocolumnar strontium-doped lead zirconate titanate (PSZT) ferroelectric thin films directly on thermal silicon dioxide. No intermediate seed or activation layers were used between PSZT and silicon dioxide. The deposited thin films have been characterised using a combination of diffraction and microscopy techniques